1. Field of the Invention
This invention relates generally to sleeve or journal bearings and more particularly to a journal bearing having a bearing body and a liner bonded to the body.
2. Related History
Sleeve or journal bearings have been employed to support rotating shafts or journals. In some bearings, a separate insert or bushing was provided to form a bearing surface. The bearing bushings were press fit into a bearing housing. In other instances, such as when a rotating shaft or journal carried significant axial loads, journal bearings were formed with a steel or bronze body having a thin liner of Babbitt metal or other bearing alloy. Such bearings were fabricated either completely around to circumscribe the shaft or journal or were split along an axial plane.
Among the requirements for bearing liner alloys were load carrying capacity, low coefficient of friction, smoothness of bearing surface, thermal conductivity, wear resistance, fatigue resistance and corrosion resistance.
Both tin based and lead based Babbitt bearing metals have been extensively used. Among the characteristics which rendered Babbitt metal suitable for bearing applications were the ability to run in quickly and to develop a smooth bearing surface. Additionally, Babbitt metal bearings were able to conform, i.e. adapt to shaft misalignment or shaft deflection and also had the attribute of imbedability, that is, a reasonable amount of foreign matter or dirt in the lubricant could be absorbed by the soft bearing material and the shaft was thus protected against scoring.
Babbitt metal has been applied as a cast in place bearing liner within a steel bearing body. To fabricate the bearing, annular grooves were formed in the bearing body and the Babbitt metal liner was cast in place. The Babbitt metal filled the grooves to lock the liner in place. This fabrication technique was relatively costly.
In addition to casting, flame or arc spray techniques for applying Babbitt metal as a bearing liner have been employed. Such techniques were utilized for applying additional liner metal to effect a repair. The bearing metal which was spray deposited provided a coating with large pores and oxide inclusions, as a result, the repaired bearing was unable to withstand the original bearing stress loads. Repaired bearings were thus utilized on applications wherein stress loads were reduced to between 50% to 70% of original specified stress.
In the case of new bearings, Babbitt metal has been applied by flame or arc spray over a steel bearing body which, like the bearing body for a cast liner, included grooves for the purpose of anchoring the liner to the body. The grooves were in the order of 0.1 to 1.0 mm deep and the inner surface of the bearing body was coated with spray deposited Babbitt metal which anchored itself into the grooves.
When tin based Babbitt metal was employed in this technique, the copper-tin compounds contained therein solidified in finely crystalline form and the formation of pores in the deposited lining was unavoidable.
Because grooves were required to be formed in the bearing body for proper adhesion, ultrasonic testing of the bond strength between the liner and the steel bearing body was precluded due to diversion and interference of the ultrasonic waves by the grooves.
Attempts have been made to adhere a spray deposited Babbitt metal liner to a steel bearing base by first tinning the surface of the bearing base. A tinned interface of FeSn or FeSn.sub.2 was formed and a bearing liner of Babbitt metal was thereafter spray deposited. Unfortunately, this technique was not suitable for producing new bearings because the quality of adhesion was inconsistent and was generally insufficient. Consequently, this technique was relegated to the repair of damaged portions of existing bearing liners.